Large flow-through boiler

ABSTRACT

A boiler includes a heating wall formed of an assembly of tubes and defines a combustion chamber, a heating partition formed of a tube system subdividing the combustion chamber and connected in parallel with the heating wall tube assembly for conducting liquid working medium, and means for adjusting the rate of flow of the working medium through the heating wall and the heating partition so that the temperature of the working medium at the outlet of the heating partition is maintained considerably below the temperature thereof at the heating wall, the heating wall comprising a heating surface tube section having a downstream end in flow direction of the working fluid, a multiplicity of parallel tube strings greater in number than the heating surfaces of the tube section and having an upstream end and a flow-through collector manifold connected between the downstream end of the heating surface tube section and the upstream end of the parallel tube strings.

United States Patent Michel LARGE FLOW-THROUGH BOILER [75] Rupprecht Michel, Erlangen,

Germany Kraftwerk Union Aktiengesellschaft, Mulheim, Germany Filed: Sept. 7, 1972 Appl. N0.: 286,704

Inventor:

[73] Assignee:

US. Cl 122/406 S, 122/451 S Int. Cl. F 22b 29/06 Field of Search 122/406 S, 406 ST, 448 S,

References Cited UNITED STATES PATENTS 10/1965 Egglesto ne l22/406 l2/l965 Wiener....

4/1966 Koch 122/406 [451 Apr. 16, 1974 Primary Examiner-Kenneth W. Sprague Attorney, Agent, or Firm-Herbert L. Lerner [5 7] ABSTRACT A boiler includes a heating wall formed of an assembly of tubes and defines a combustion chamber, a heating partition formed of a tube system subdividing the combustion chamber and connected in parallel with the heating wall tube assembly for conducting liquid working medium, and means for adjusting the rate of flow of the working medium through the heating wall and the heating partition so that the temperature of the working medium at the outlet of the heating partition is maintained considerably below the temperature thereof at the heating wall, the heating wall comprising a heating surface tube section having a downstream end in flow direction of the working fluid, a multiplicity of parallel tube strings greater in number than the heating surfaces of the tube section and having an upstream end and a flow-through collector manifold connected between the downstream end of the heating surface tube section and the upstream end of the parallel tube strings.

4 Claims, 3 Drawing Figures LARGE FLOW-THROUGH BOILER The invention relates to a large boiler and, more particularly, to a boiler operated with pulverized-coal firing and dry ash removal, such as a so-called oncethrough boiler, wherein the combustion chamber of the boiler is subdivided by at least one partition cooled by working medium.

Boilers of this general type are known and have a heating wall formed of heating surface members preferably comprising an assembly of coiledtubes and defining a combustion chamber, a heating partition formed of a tube system subdividing the combustion chamber and connected in parallel with the heating wall tube assembly for conducting liquid working medium, and means for adjusting the flow rate of the working medium through the heating wall and the heating partition so that the working medium is at saturated steam temperature at the outlet of the heating partition tube system and is at a higher temperature in the heating surface members of the heating wall such as at steam temperatures in the range of 400 to 450 C.

In furthering the development of the heretofore known principle. the invention of the instant application calls for the heating wall to comprise a heating surface tube section having a downstream end in flow direction of the working fluid,'a multiplicity of parallel tube strings greater in number than the heating surfaces of the tube section-and having an upstream end and a flow-through collector manifold connected between the downstream end of the heating surface tube section and the upstream end of the parallel tube strings.

More specifically, in accordance with the invention, downcomer tubes connect the upper end of the heating partition tube system to a flow-through collector manifold for conducting discharging steam thereto, the manifold being connected between the heating surface members of the heating wall at a'location at which a transfer to a multiplicity of parallel tube strings greater in number to the number of heating surface members is effected. In this manner, when greatly heating the working medium in the heating surface members of the heating wall, an increased flow-through of working medium in the upper region of the heating wall surface members can be effected. because the complete flow of the working medium, instead of a partial flow thereof, can be applied thereto in order that unduly high thermal loadings or stresses should counteract one another in the section of heating surface members. i

This measure can be carried out analogously both with once-through boilers as well as with repeated flowthrough boilers. In once-through boilers, the partition is drawn upwardly through the connection heating surfaces whereas, in twice or more flow-through boilers, the partition is passed through the boiler cover. Furthermore, the invention of the instant application has special significance for boilers wherein the heating surface members of the heating wall defining the combustion chamber have a helical coil construction and are suited especially for a type of construction wherein the helical coil ends at about two-thirds of the height of the combustion chamber and, downstream of a flowthrough collector manifold in flow direction of the working medium, continues upwardly with vertical tubing. In accordance with a further feature of the invention, means are provided to control or regulate the mass flow of the working medium through the partition Although the invention is illustrated and described herein as embodied .in large flow-through boilers, it is nevertheless not intended to be limited to the details shown since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope 'and range of equivalents of the claims.

The construction and method of operation of the invention, however, togetherwith'additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic view of the boiler of the invention;

FIG. 2 is an enlarged fragmentary view of FIG. I showing a front elevation thereof; and

FIG. 3 is a side elevational view of FIG. 2.

Referring now to the drawing and first, particularly to FIG. 1 thereof, there is shown therein a feed pump 7 which feeds working medium, such as water through the heating surfaces of an economizer 8, the working medium being divided into two partial flows either upstream or downstream of the economizer heating surfaces. With the aid of a control or regulating valve 9, the mass flow of working medium to heating surfaces of an outer wall of tubes defining a combustion chamber is adjusted, and through a control or regulating valve 10, the mass flow of the working medium to the heating surfaces of a partition formed of vertical tubes and subdividing the combustion chamber, is adjusted. Whereas the valve 9 could generally be dispensed with, in most cases, a throttling action effected with the aid of the valve 10 is necessary. The combustion chamber partition, in the illustrated embodiment, is represented by heating surfaces 4, provided with vertical tubes having an inlet distributor manifold 5 and an outlet collec-- tor manifold 6. Analogously, instead of a single combustion chamber partition, several of such partitions can naturally be used.

The outer wall heating surfaces are formed, in the illustrated embodiment, by a coiled tube system 51 wherein, for example," adjacent tubes are welded gastightly together. The coiled tube system 51 rising upwardly from an inlet distributor manifold 52 do not extend to the top of the combustion chamber, but end rather at an intermediate flow-through collector manifold 53, from which vertical tube 54 extend upwardly to'an outlet collector manifold-55 at the top of the combustion chamber. Steam discharging from the'manifold 55 pass through individual lines 56 to'a mixing'vessel 57 and therefrom to heating surfaces of a superheater The steam generated inthe partition heating surfaces 4, are conducted from the collector manifold 6 thereof to the flowdhrough collector manifold 53 of the outer wall heating surfaces 51' through suitable downcomer tubes 58, 59 and 60 for downwardly passing the steam from the outlet collector manifold'6'of the combustion chamber partition to the flow-through collector manifold 53 of the outer wall heating surfaces. The mass flow through the partition is controllable by adjusting the valves 9 and 10 so that the enthalpy of the steam in the collector manifold 6 is the same as that of the steam in the flow-through collector manifold 53. In this manner, the vertically extending tubes are traversed by the entire quantity of working medium.

In the diagrammatic sectional views of FIGS. 2 and 3 which are perpendicular to one another, the disposition of the tubes in the vicinity of the flow-through collector manifold 53 is shown in greater detail. As can be readily seen therein, at the level of the flow-through collector manifold 53, the inclined riser tubes 61 of the coiled tube system are bent vertically upwardly so that short tube lengths 62 extend vertically upwardly. At 10- cations 63, as seen more clearly in FIG. 3, the vertically rising tubes extend downwardly with tube lengths 64 to the flow-through collector manifold 53 and return to the location 63 from which they extend as vertical tubes 66 to the upper outlet collector manifold 55 in the manner of the vertical tube system 54 shown in FIG. 1. Moreover,'in the gaps or spaces between the riser tube lengths 62, additional tubes 67 and 68 extend upwardly between the flow-through collector manifold 53 and the outlet manifold 55. In this manner, with the aid of finned tubes, a gas-tight, welded closure of the combustion chamber wall formed by the tubes 62, 66, 67, 68 is facilitated. The downcomer tubes 58, 59 and 60 from the combustion chamber partition heating surfaces 4 extend from above into the flow-through collector manifold 53.

I claim:

l. A boiler comprising a heating wall formed of an assembly of tubes and defining a combustion chamber, a heating partition formed of a tube system subdividing said combustion chamber and connected in parallel with part of said heating wall tube assembly for conducting liquid working medium, and means for adjust- 4 ing the rate of flow of the working medium through the tubes of said heating wall and said heating partition so that the temperature of the working medium at the outlet of said heating partition is maintained considerably below the temperature thereof at said heating wall, said heating wall comprising a heating surface tube section having a downstream end in flow direction of the working fluid, a multiplicity of parallel tube strings greater in number than the heating surfaces of said tube section and having an upstream end and a flow-through collector manifold connected between said downstream end of said heating surface tube section and said upstream end of said parallel tube strings.

2. A boiler according to claim 1 wherein the working medium is water, and said means for adjusting the rate of flow of the working medium through said heating wall and said heatingpartition is effective for maintaining the temperature of the working medium at the outlet of said heating wall within the range'of 400 and 450 C and the temperature of the working medium at the outlet of said heating partition at saturated steam temperature. v

3. A boiler according to claim 1 wherein said heating surface tube section is formed of coiled tubes, and said parallel tube strings extend in vertical direction, said flow-through collector manifold being disposed be-' tween said coiled tubes and said vertical tube strings.

manifold. 

1. A boiler comprising a heating wall formed of an assembly of tubes and defining a combustion chamber, a heating partition formed of a tube system subdividing said combustion chamber and connected in parallel with part of said heating wall tube assembly for conducting liquid working medium, and means for adjusting the rate of flow of the working medium through the tubes of said heating wall and said heating partition so that the temperature of the working medium at the outlet of said heating partition is maintained considerably below the temperature thereof at said heating wall, said heating wall comprising a heating surface tube section having a downstream end in flow direction of the working fluid, a multiplicity of parallel tube strings greater in number than the heating surfaces of said tube section and having an upstream end and a flow-through collector manifold connected between said downstream end of said heating surface tube section and said upstream end of said parallel tube strings.
 2. A boiler according to claim 1 wherein the working medium is water, and said means for adjusting the rate of flow of the working medium through said heating wall and said heating partition is effective for maintaining the temperature of the working medium at the outlet of said heating wall within the range of 400* and 450* C and the temperature of the working medium at the outlet of said heating partition at saturated steam temperature.
 3. A boiler according to claim 1 wherein said heating surface tube section is formed of coiled tubes, and said parallel tube strings extend in vertical direction, said flow-through collector manifold being disposed between said coiled tubes and said vertical tube strings.
 4. A boiler according to claim 3 wherein said flow rate adjusting means includes means for controlling mass flow of the working medium through said heating partition tube system so that the enthalpy of the working medium at the outlet of said heating partition tube system is the same as in said flow-through collector manifold. 